A comparison of NH3, PH3, PH2, OH2 and SH as ligands in iridium(III) complexes
Abstract
The aqua complex trans,mer-[IrCl2(H2O)(PMe2Ph)3][ClO4] of known crystal structure contains a highly labile H2O ligand which is readily substituted. The corresponding ammonia and phosphine complexes trans,mer-[IrCl2(EH3)(PMe2Ph)3][ClO4](E = N or P), synthesised from the aqua complex, are inert and have been structurally characterised and compared with the aqua species. The cationic complex containing PH3 is readily deprotonated, but not the one with NH3, to give the structurally characterised neutral complex trans,mer-[IrCl2(PH2)(PMe2Ph)3]. The Ir–PH3 bond is significantly shorter than the Ir–PH2 bond and there are clear conformational changes resulting from deprotonation. Replacement of H2O by H2S leads to spontaneous deprotonation and formation of trans,mer-[IrCl2(SH)(PMe2Ph)3](crystal structure also reported). Analysis of the geometries of trans,mer-[IrCl2L(PMe2Ph)3][ClO4](L = H2O, NH3 or PH3) and of trans,mer-[IrCl2X(PMe2Ph)3](X = H, Cl, SH or PH2) has allowed the properties of these ligands, in particular their trans influences, to be assessed.